This is a well known bug in 17.8.11. The "Advisor" wrongly advises the true http/2 status and... it's never been fixed.
We asked the question elsewhere i.e. if this specifc Advisor bug had been fixed for Obsidian but our question wasn't answered. To be fair, quite a few bugs that are still in 17.8.11 have, actually, been fixed in Obsidian, or so the officlal Plesk records to date, do indicate. Your post would indicate that this one has not been fixed... so maybe that's why we never got an answer We haven't upgraded to Obsidian - yet - as we're still reading through other people's experiences so far.